The present invention relates generally to the art of engine driven welders. More specifically, it relates to engine driven welders having an engine that idles when no welding is occurring, and that provide an OCV adequate for starting an arc and/or wire feeder.
Engine driven welding power supplies are well known, and may be driven either by a DC generator or an AC generator (also called an alternator-rectifier). An AC generator generally includes, in addition to an alternator, a reactor followed by rectifiers to provide a DC output.
Often, the output is controlled in welding power supplies using feedback. For example, a field current control includes comparing field current to a set point, and adjusted the field current in response to deviations therefrom.
Another prior art design receives welding current and/or welding voltage feedback, and controls the field current to produce a desired output. U.S. Pat. No. 5,734,147, issued Mar. 31, 1998 to the assignee of the present invention, and entitled Method And Apparatus For Electronically Controlling The Output Of A Generator Driven Welding Power Supply, describes such a control, and is hereby incorporated by reference. Another example of a known engine driven welding power supply with field current control is the Miller Big Blue 400(trademark). Such prior art engine driven power supplies can be operated to provide a CC or a CV output. The prior art engine-driven welding power supplies, and their field current controllers, generally perform well.
It is desirable to allow the engine to idle at a low engine speed during times when welding is not being performed. This saves fuel, reduces noise, and extends the life of the engine and reduces the OCV. However, idling is not done in the CV mode because such an engine-driven welding power supply is often operated with a wire feeder that uses the welding voltage to power the feeder motor, such as the Miller S-32P(trademark) portable wire feeder. A low OCV does not provide sufficient power to reliably start such a wire feeder (i.e., provide enough voltage for the torque needed to start the electric motor in the wire feeder). Thus, to maintain the output voltage (OCV) at a high enough magnitude to reliably start the wire feeder, the engine is operated at a running rpm (not an idle rpm), even when welding is not being performed.
Accordingly, an engine driven welding power supply that idles when not welding is desirable. Preferably, such an engine driven welding power supply will provide an open circuit voltage sufficient to reliably start a wire feeder (i.e., have enough voltage for the torque needed to start the electric wire feed motor), and to reliably start the arc.
According to a first aspect of the invention a generator driven welding power supply includes a generator driven by an engine, and an electronic field controller. The generator includes a field winding and a welding output winding. The electronic field controller is connected to the field winding and has an engine feedback input. The controller also has a voltage boost circuit that is responsive to the engine feedback input. The engine feedback input receives a signal representative of the engine speed.
The electronic field controller includes a CV controller, and the welding output winding is disposed to provide a welding voltage output in one embodiment.
An RPM sensor senses the RPM of the engine, and is connected to the engine feedback input, and the RPM sensor includes an idle sense circuit in various alternatives.
The engine includes a speed input and a welding output feedback circuit is disposed to provide an output feedback signal indicative of the presence or absence of a welding arc in another embodiment. An engine speed controller is connected to the engine speed input, which receives the output feedback signal.
A wire feeder is disposed to provide wire to an arc in yet another embodiment. The wire feeder includes a motor that feeds wire in response to a wire feed input power. The wire feeder receives the welding voltage output as the wire feeder input power, and provides power to the arc.
The apparatus voltage boost circuit increases the field current, and thus the magnitude of the welding voltage output is increased, in response to the engine speed being below a threshold in yet another alternative.
According to a second aspect of the invention a method of providing a welding power output includes running an engine, and driving a generator with the engine to produce an electrical output. A field current in a generator field winding is electronically controlled, thereby controlling the electrical output. The engine speed is sensed, and the field current is boosted when the engine speed drops below a threshold.
The speed of the engine is reduced when there is no welding arc in one embodiment. Wire is fed to the arc from a wire feeder, and power for the wire feeder comes from the electrical output in another embodiments
The electronic field current control includes controlling the field current to provide a CV output in another alternative.
Sensing the engine speed includes sensing the RPM of the engine, and/or boosting the field current when the engine idles in various embodiments.
According to a third aspect of the invention, a generator driven welding power supply includes an engine and a generator connected to and driven by the engine. The generator includes a welding output winding disposed to provide power to a welding arc. A CV controller is connected to the welding output and the generator. A welding output feedback circuit provides an output feedback signal indicative of the presence or absence of a welding arc, and the engine idles in response to a feedback signal indicative of the absence of an arc.
According to a fourth aspect of the invention, a method of providing a welding power includes driving a generator with an engine and producing a welding output. The generator is controlled to provide a CV output and the presence or absence of a welding arc is sensed. The engine is caused to idle in the event the absence of the arc is sensed.
According to a fifth aspect of the invention, a method of providing a welding output includes a generator driven by an engine. The generator includes a field winding and a welding output winding. An electronic field controller is connected to the field winding, and has an arc feedback input and a voltage boost circuit responsive to the arc feedback input, The arc feedback input is disposed to receive a signal representative of a parameter of the arc.
The voltage boost circuit includes a circuit disposed to increase the field current in response to the arc feedback input indicating the arc current is less than a threshold and/or an arc sensor senses the presence or absence of the arc, and is connected to the arc feedback in other alternatives. The threshold may be is less than normal welding current.
According to a fifth aspect of the invention, a method of providing a welding power output includes running an engine and driving a generator with the engine to produce an electrical output. A field current in a generator field winding is electronically controlled to control the electrical output. The field current is boosted in response to a selected arc parameter.
The arc parameter is the presence or absence of the welding arc in one embodiment.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.